This invention relates to a method and apparatus for the removal of anode butts or anode remnants and stripping thimbles from anodes such as those used in the electrolytic smelting of aluminiums.
In the electrolytic smelting of metals such as aluminium, the cathode is located in the bottom and lower side regions of the cell and a carbon anode block is suspended or supported by yoke stubs attached to the anode rod. The yoke stubs have cast iron thimbles fitted at their lowermost end and the thimbles are cast within recesses in the carbon anode block. During operation of the smelting cell the carbon anode is consumed requiring regular replacement of the anode block.
To replace the anode block, it is necessary to remove the anode remnants or butts and the cast iron thimbles from the anode yoke stubs. For the economics of the smelting operation, it is highly desirable that the anode butts are removed, crushed and the carbon reclaimed for use in replacement carbon anode blocks.
In the prior art, the thimbles and anode butts are removed by a downwardly acting stripper. Since the main support for the anode rod and anode butt is the overhead transport crane; additional clamping device have been employed to resist the downward forces required to strip the anode butt and thimble from the anode yoke stubs.
In GB 1269809, an anode stripping apparatus is disclosed in which the anode rod is clamped in a clamping device consisting of two hydraulically operated pistons. Hydraulic strippers act vertically downwardly on the anode butt to strip the butt from the stub. Scrappers are provided on the downwardly acting strippers to remove the thimble from the stub.
During the downward operation of the stripper, the anode rod is held in position and supported by the clamping device acting laterally on the rod. Since a large force needs to be applied by the clamping device to resist the downward forces of the stripper, damage to the anode rod and a shortened operating life is inevitable.
The apparatus as disclosed in EP 191,954 and U.S. Pat. No. 4,442,593 also rely on downwardly acting hydraulic rams to break the anode butt from the anode stub.
Australian Patent No. 565330 and GB 2,108,530 relate to holding device for an anode stub to secure the anode in position during cleaning of the anode.
In other prior art methods, the steps of anode block removal and thimble stripping have been carried out in separate operations, on separate apparatus and at separate locations thereby increasing the space required for the operations and the capital cost of equipment.